Sino-Vietnamese War

The Sino-Vietnamese War was fought from 17 February to 16 March 1979 when China invaded northern Vietnam in retaliation for the Vietnamese invasion of Cambodia a year earlier.

China had separated from the rest of the Eastern Bloc when, under Deng Xiaoping, it began to open trade with the West and establish friendly relations with the United States, leading to rivalry with the Soviet Union for the leadership of the communist bloc. On 3 November 1978, the USSR and Vietnam signed a 25-year mutual defense treaty as a part of the USSR's initiative to contain China. In January 1979, Deng Xiaoping informed President of the United States Jimmy Carter that he would launch a retaliatory attack on Vietnam; on 15 February, he publicly declared that, due to the Vietnamese invasion of Maoist Cambodia, the mistreatment of ethnic Chinese people in Vietnam, and the Vietnamese occupation of the disputed Spratly Islands, China would conduct a limited attack on Vietnam. China also prepared for war with the USSR by putting all 1.5 million People's Liberation Army troops on the Sino-Soviet border on emergency war alert and evacuating 300,000 civilians from the border region.

On 17 February 1979, 200,000 PLA troops and 550 tanks under Xu Shiyou invaded Vietnam. The 100,000 PAVN troops and 150,000 Vietnamese militia were supplied with 400 Soviet-made tanks, 500 mortar and air defense artillery, 50 BM-21 rocket launchers, 400 portable SAM missiles, 800 anti-tank missiles, 20 jet fighters, and 8,000 advisers. The Chinese advanced 9 to 12 miles into Vietnam in the provinces of Cao Bang, Lao Cai, and Lang Son, and the Vietnamese army utilized guerrilla tactics to hold back the Chinese invasion. The first PLA attack wave lost its momentum, so eight more PLA divisions were sent in to join the battle. On 6 March, after three days of bloody house-to-house fighting, the Chinese took Lang Son and occupied Sa Pa, crushing several Vietnamese regular units. By 6 March, the Chinese were threatening Hanoi, but they declared that their punitive mission had been achieved, and they destroyed all local infrastructure and housing as they withdrew to the border, even stealing local livestock to destroy the economy of Vietnam's northern provinces.

Both sides claimed victory, as China claimed to have succeeded in punishing Vietnam and turning international opinion against Vietnam's occupation of Cambodia, while Vietnam claimed to have repelled the Chinese invasion using mostly border militias. In the aftermath of the war, 20,468 Maoist members of the Communist Party of Vietnam were expelled from the party, and the Vietnamese government partially resettled ethnic Chinese and Hmong people from the north to the south to prevent them foom assisting any further Chinese invasions. In 1989, Vietnam fully withdrew from Cambodia, and Vietnam and China fully normalized ties in November 1991.